In recent years, coil components such as transformers, choke coils or the like used in various kinds of civilian electronic equipment, have been made thinner and shorter, and further have been desired to enhance their electric characteristics such as a low loss, low heat generation, high efficiency, and a low leakage flux. In this situation, it has been also required that they have structures which enhance productivity, and accordingly, a method of stamping iron cores, which is highly productive and economical, has been desired.
Among conventional coil components, a transformer as a conventional example, will be hereinbelow explained with reference to FIGS. 22 to 27. Referring FIGS. 22 and 23, windings 3 composed of a primary winding and a second winding are wound on a coil bobbin 2 having flanges at opposite ends thereof, and an E-shaped laminate iron core 4 having a predetermined thickness is inserted in the coil bobbin 2 while an I-shaped laminate iron core 5 having a predetermined lamination thickness is arranged so as to abut against the magnetic leg end side of the E-shaped laminate iron core 4. Then, the abutting parts of both iron cores 4, 5 are fixed together by welding or by using a metal frame or the like so as to form the transformer.
With the above-mentioned arrangement, as shown in FIGS. 24(a) and (b), the space required for the windings is inevitably small due to (a) the previous provision of a clearance A between (1) the windings 3 or the outer peripheral part of the coil bobbin 2 and (2) both outside magnetic legs of the E-shaped laminate iron core 4, which depends upon the direction of insertion of the E-shaped laminate iron core into the coil bobbin 2, and the clearance a between (1) the center hole of the coil bobbin 3 and (2) the center magnetic leg of the E-shaped laminate iron core 4, and (b) the necessity of a clearance B for deformation of the coil bobbin 2 caused by winding tension, or the like. Accordingly, this hinders the transformer from being minaturized and made thinner.
Further, with the provision of the above-mentioned clearances A and B, air layers are present between the windings 3 or the coil bobbin 2 and the E-shaped laminate iron core 4, causing heat radiation to deteriorate so that the temperature rise becomes steep and further possibly causing vibration. Accordingly, the reliability of the transformer is inferior.
Further, due to the use of the E-shaped laminate iron core 4 and the I-shaped laminated iron core 5 for the iron core of the transformer, the abutting parts of both iron cores 4, 5 are orthogonal to the magnetic flux so that the abutting parts serve as a magnetic gap. Accordingly, the leakage of magnetic flux through the abutting parts becomes excessive, resulting in difficulty in lowering the leakage of magnetic flux.
Further, since the clearances should be taken by a large degree as mentioned above, the windings 3 have to be wound in order or in line-up so as to effectively use the winding space at its maximum. Accordingly, the winding requires a large amount of manhours, and further, the cost of the winding machine therefore becomes expensive.
Further, as shown in FIG. 25; if the insertion angle of the E-shaped laminate iron core 4 into the coil bobbin 2 goes out of order, or if the outer diameter of the windings becomes excessively large as shown in FIG. 30, a corner of one of the magnetic legs of the E-Shaped laminate iron is likely to damage the outer surface of the windings 3 upon insertion of the E-shaped laminate iron core 4, causing deterioration of insulation. Accordingly, it is inferior with respect to safety.
As mentioned above, since the risk of increase in the diameter of the windings 3 would often occur, as shown in FIG. 27, the windings 3 are pressed on opposite sides with the use of winding shaping tools 6 so as to put the diameter of the windings in order after the formation of the windings 3. However, this shaping causes cracking and deformation of the coil bobbin 2 so as to incur secondary inferiority such as breakage or inferior insulation of the windings 3, that is, serious problems are raised with respect to reliability.
The present invention is devised in order to eliminate the above-mentioned disadvantages inherent to the conventional arrangement, and accordingly, one object of the present invention is to provide a coil part which is lightweight, thin and short, and which is excellent in electrical characteristics.